Ultrasound flow measurement and particularly color flow mapping (CFM) systems provide a valuable tool for medical diagnosis. These techniques primarily exploit the Doppler effect which, despite its great success, results in two fundamental drawbacks: (1) the inability to measure non- axial flow components and (20 the inability to measure high velocities at great depth. We propose to develop a system which (10 provides the capability for measuring the transverse components of flow velocity and (2) can measure very high velocities, both with high lateral resolution. The technique uses a newly developed multi-beam acoustic lens or lens system in which the separations between the acoustic foci are pre-determined by the lens or lens system design. The ultrasound signals scattered from these foci are cross-correlated, resulting in flow velocity measurement. In Phase I this has been demonstrated by using a dual beam acoustic lens. During Phase II, we propose to develop a triple beam system and to combine a newly emerging time-domain correlation technique (for obtaining an axial component estimate) for a complete three-directional (3-D) velocity vector imaging system. We believe such a system will accurately detect flow disturbance arising from, for example, atherosclerotic lesions.